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Computer Networksknowledge~5 mins

DNS poisoning in Computer Networks - Cheat Sheet & Quick Revision

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Recall & Review
beginner
What is DNS poisoning?
DNS poisoning is a cyber attack where false information is inserted into a DNS server's cache. This causes users to be redirected to fake websites instead of the real ones they want to visit.
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beginner
How does DNS poisoning affect internet users?
It can trick users into visiting fake websites that look real. These fake sites can steal personal information like passwords or install harmful software.
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beginner
What is a DNS cache?
A DNS cache is a temporary storage on a computer or server that saves recent website address lookups to speed up future visits.
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intermediate
Name one common method to prevent DNS poisoning.
Using DNS Security Extensions (DNSSEC) helps verify that DNS responses are authentic and have not been tampered with.
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intermediate
Why is DNS poisoning dangerous for businesses?
It can lead to loss of customer trust, theft of sensitive data, and damage to the company's reputation if customers are redirected to fraudulent sites.
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What does DNS stand for?
ADomain Name System
BData Network Service
CDigital Name Server
DDomain Number Service
What is the main goal of DNS poisoning?
ATo block access to websites
BTo speed up internet browsing
CTo redirect users to fake websites
DTo improve website security
Which of these helps protect against DNS poisoning?
ADisabling cookies
BUsing DNSSEC
CUsing a VPN
DClearing browser history
Where is DNS cache stored?
AOn your computer or DNS server
BOnly on the website server
CIn your email inbox
DOn your internet provider's billing system
What can happen if you visit a fake website due to DNS poisoning?
AYour computer will automatically update
BYou will get free software
CYour internet speed will increase
DYou might lose personal information
Explain in your own words what DNS poisoning is and why it is a security risk.
Think about how wrong address info can trick you online.
You got /3 concepts.
    Describe one way to protect against DNS poisoning and how it works.
    Consider how websites prove they are real.
    You got /3 concepts.

      Practice

      (1/5)
      1. What is the main goal of DNS poisoning in computer networks?
      easy
      A. To block access to certain websites
      B. To redirect users to fake websites by giving wrong IP addresses
      C. To encrypt DNS queries for security
      D. To speed up the DNS lookup process

      Solution

      1. Step 1: Understand DNS function

        DNS translates website names into IP addresses so computers can find websites.

      2. Step 2: Identify DNS poisoning effect

        DNS poisoning gives wrong IP addresses, sending users to fake sites instead of real ones.

      3. Final Answer:

        To redirect users to fake websites by giving wrong IP addresses -> Option B

      4. Quick Check:

        DNS poisoning = Redirect to fake sites [OK]
      Hint: DNS poisoning tricks DNS to give wrong addresses [OK]
      Common Mistakes:
      • Thinking DNS poisoning speeds up browsing
      • Confusing DNS poisoning with encryption
      • Believing it blocks websites instead of redirecting
      2. Which of the following is a correct way to describe DNS poisoning?
      easy
      A. It modifies DNS cache with false information
      B. It encrypts DNS queries to protect privacy
      C. It speeds up DNS resolution by caching
      D. It blocks DNS requests from unknown sources

      Solution

      1. Step 1: Recall DNS poisoning mechanism

        DNS poisoning involves changing DNS cache entries to wrong IP addresses.

      2. Step 2: Match description to options

        Only It modifies DNS cache with false information correctly states DNS poisoning modifies DNS cache with false info.

      3. Final Answer:

        It modifies DNS cache with false information -> Option A

      4. Quick Check:

        DNS poisoning = false DNS cache entries [OK]
      Hint: DNS poisoning changes DNS cache to wrong info [OK]
      Common Mistakes:
      • Confusing poisoning with encryption
      • Thinking it speeds up DNS
      • Assuming it blocks requests
      3. Consider this scenario: A user tries to visit example.com. Due to DNS poisoning, the DNS cache returns the IP 192.0.2.123 instead of the real IP 93.184.216.34. What is the likely result?
      medium
      A. The user is redirected to a fake website at IP 192.0.2.123
      B. The DNS query fails and the website doesn't load
      C. The user reaches the real example.com website safely
      D. The user's browser automatically blocks the connection

      Solution

      1. Step 1: Understand DNS poisoning effect on IP

        The DNS cache gives a wrong IP (192.0.2.123) instead of the real one (93.184.216.34).

      2. Step 2: Predict user experience

        The user is sent to the wrong IP, likely a fake website pretending to be example.com.

      3. Final Answer:

        The user is redirected to a fake website at IP 192.0.2.123 -> Option A

      4. Quick Check:

        Wrong IP from DNS = fake site visit [OK]
      Hint: Wrong IP from DNS means fake site shown [OK]
      Common Mistakes:
      • Assuming user reaches real site
      • Thinking DNS query fails
      • Believing browser blocks automatically
      4. A network admin notices users are being redirected to suspicious sites. They suspect DNS poisoning. Which action will help fix this issue?
      medium
      A. Turn off the internet connection temporarily
      B. Disable the firewall to allow all traffic
      C. Change all user passwords immediately
      D. Clear the DNS cache on affected devices and servers

      Solution

      1. Step 1: Identify how DNS poisoning affects devices

        DNS poisoning corrupts DNS cache with wrong IP addresses causing redirection.

      2. Step 2: Choose corrective action

        Clearing DNS cache removes false entries, restoring correct address resolution.

      3. Final Answer:

        Clear the DNS cache on affected devices and servers -> Option D

      4. Quick Check:

        Fix DNS poisoning by clearing DNS cache [OK]
      Hint: Clear DNS cache to remove poisoned entries [OK]
      Common Mistakes:
      • Disabling firewall worsens security
      • Changing passwords doesn't fix DNS
      • Turning off internet is impractical
      5. A company wants to protect its users from DNS poisoning attacks. Which combined approach is best to reduce risk?
      hard
      A. Manually edit hosts files on all user devices
      B. Only use public Wi-Fi networks and disable firewalls
      C. Use DNSSEC to verify DNS data and configure trusted DNS servers
      D. Rely solely on antivirus software for protection

      Solution

      1. Step 1: Understand DNSSEC and trusted DNS servers

        DNSSEC adds digital signatures to DNS data to verify authenticity. Trusted DNS servers reduce risk of poisoning.

      2. Step 2: Evaluate options for protection

        Use DNSSEC to verify DNS data and configure trusted DNS servers combines verification and trusted sources, effectively reducing DNS poisoning risk.

      3. Final Answer:

        Use DNSSEC to verify DNS data and configure trusted DNS servers -> Option C

      4. Quick Check:

        DNSSEC + trusted DNS = strong DNS poisoning defense [OK]
      Hint: Use DNSSEC and trusted servers to stop poisoning [OK]
      Common Mistakes:
      • Thinking public Wi-Fi is safe
      • Manually editing hosts is impractical
      • Relying only on antivirus misses DNS attacks
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